Former college friends-- Ron (Jeremy Piven), Jonathan (Rob Lowe), Richard (Thomas Jane), and Tim (Christian McKay) reunite in Big Sur during Spring break to celebrate Tim's 44th birthday. Each of the men enjoy some degree of professional success but are unfulfilled with their lives: Ron is a rich stockbroker, but is currently facing indictment from the SEC for embezzlement. Jonathan runs a successful medical practice, but all of his patients are wealthy drug addicts, he and his wife are divorced, and their young son identifies more with his mother's new husband than with Jonathan. Richard is a published author, but he has only written one book and now teaches high school English. Tim, an open bisexual, was until recently living in a happy polyamorous relationship with a man and woman, until accidentally causing the fatal car crash that killed them.
After days of partying at a beach side mansion, during which the men consume massive quantities of drugs provided to them by Jonathan, they head into town for food and to pick up women. Richard convinces a young waitress to bring her friends back to the house. Tim engages in a three-way with two of the revelers, during which they agree to role play the parts of Tim's dead lovers. Sometime in the middle of the night, Tim hangs himself in the shower. Richard, Ron, and Jonathan find him the next morning, along with a note he left behind. The note contains the text of a suicide pact the men made in 1986, promising that they would kill themselves together if they found life unfulfilling in middle age. Afraid that the police will find the note and blame them for Tim's death, they bury him on the beach behind the house.
Going into town for lunch, the men eat at a restaurant where an elderly man goes into cardiac arrest. Jonathan saves his life, drawing the attention of police Officer Boyde (Carla Gugino). Coming to the house to thank Jonathan, Boyde encounters an inebriated and agitated Ron. Believing that Boyde knows something is wrong, Ron attempts to get her to leave, raising Boyde's suspicions.
That night, Ron calls home and finds out that the authorities are awaiting his return. He goes to an airport in an attempt to flee, but cannot bring himself to board the plane. He returns to the house and gets drunk, telling Richard that he is frustrated with where his life has ended up and no longer wants to live. Richard agrees to help him end his suffering and smothers him to death with a pillow. The next morning, Richard and Jonathan bury Ron beside Tim.
Richard and Jonathan go into town to party more, where Richard provokes two young men into beating him up. Jonathan, having decided to end his life, calls his son, asking the boy to promise him to remember who his real father was. After Jonathan's ex-wife interrupts, he uses a stethescope to make a tourniquet and gives himself a fatal overdose of intravenous sedative.
The next morning Boyde arrives at the house to check in on the men, the bar fight and Ron's suspicious behavior leading her to believe that something criminal is occurring. Entering the mansion, she finds that Richard has covered the inside of the house in artistic recreations of the text of the suicide pact. Richard tells that his friends are dead and then flees in a sports car, leading Boyde on a high speed chase to the Point Sur Lighthouse. When Boyde arrives, she finds Richard's car with the suicide pact on the front seat and Richard near the edge of the cliffs above the ocean. Boyde attempts to talk Richard away from the edge, but Richard states he would "miss his friends too much" and jumps while Boyde looks on in shock. The film ends on a close up of the suicide pact and the four friends each narrating a line.